we are tyco integrated security. and we are sharper. ♪ (train horn) vo: wherever our trains go, the economy comes to life. norfolk southern. one line, infinite possibilities. hwelcome back.. nice to see you again! hey! i almost didn't recognize you without the suit. well, this is my weekend suit. weekend getaways just got better. well, enjoy your round! alright, thanks! save a ton on our best available rate when you book early and feel the hamptonality. >>> we have new details tonight about what motivated dzhokhar tsarnaev and his brother tamerlan to allegedly carry out the boston marathon terror attack in which three were killed, more than 260 were injured. now, according to a government official, dzhokhar tsarnaev has said that the war in afghanistan and iraq were the reason that they decided to set off the deadly bombs. he has also told investigators that the brothers were self-radicalized. again, this is what he's saying. but how could these two chechen immigrants have become jihadists? our david mattingly is "